The explosions at the supposed nuclear test site deep in the mountains were centered on three tunnels into the underground site and a number of observation towers in the area.

The planned closing of the Punggye-ri site was previously announced by dictator Kim Jong Un ahead of the planned summit with President Trump that has been slated for June 12. It was seen as a goodwill gesture ahead of the meeting, but still wouldn’t meet U.S. demands for complete denuclearization.

Satellite images obtained by 38 North earlier this month appeared to show the regime demolishing buildings and removing mining carts at the site. A shed and engineering office building at the site’s north portal, where the last five nuclear tests were conducted, were gone in those images.

Although North Korea committed to closing Punggye-ri’s test site, another facility could be used to continue the country’s nuclear weapons program. Yongbyon nuclear complex, located about 64 miles north of Pyongyang, has a new reactor that could produce weapons-grade plutonium. Pyongyang insists it is being used to produce electricity for its citizens.

The regime began operating its first nuclear reactor at the complex in the 1980s, The New York Times reported. In 2007, North Korea shut down facilities in the complex as part of an agreement during six-nation nuclear talks. A cooling tower was demolished at the complex as a “gesture of good faith,” but did little to completely shut down the site.

Satellite images in 2010 showed the regime was beginning to construct a new reactor. Officials announced three years later that it would restart the reactor at Yongbyon, the same year North Korea conducted a nuclear test. In February, satellite images appeared to show signs the five-megawatt reactor was operating.

Earlier Thursday, North Korea threatened to back away from the much-anticipated summit with the U.S. and called Vice President Pence a “political dummy.” Pence told Fox News’ Martha MacCallum on Monday that North Korea asked for the meeting, prompting the harsh response from Pyongyang.

“As a person involved in the U.S. affairs, I cannot suppress my surprise at such ignorant and stupid remarks gushing out from the mouth of the U.S. vice president," North Korea's vice foreign minister, Choe Sun Hui, said in a statement released by state media, according to The Wall Street Journal.

Whether the U.S. "will meet us at a meeting room or encounter us at nuclear-to-nuclear showdown is entirely dependent upon the decision and behavior of the United States," Choe said, according to South Korea's Yonhap News Agency.

Choe said she'd suggest Kim reconsider the summit if "the U.S. offends against our goodwill and clings to unlawful and outrageous acts."

Fox News’ Katherine Lam and Nicole Darrah and the Associated Press contributed to this report.

Ryan Gaydos is an editor for Fox News. Follow him on Twitter @RyanGaydos.